具有固定长度的元组的子集

Question

我希望有一个函数subset(("A","b","C","D"),3)，它提供以下输出：

("A","b","C")
("A","b","D")
("A","C","D")
("b","C","D")

我如何在python 3中执行此操作？

Answer 1

为此目的明确构建了itertools.combinations函数：

>>> from itertools import combinations
>>> list(combinations(("A","b","C","D"), 3))
[('A', 'b', 'C'), ('A', 'b', 'D'), ('A', 'C', 'D'), ('b', 'C', 'D')]
>>>

来自docs：

  

itertools.combinations(iterable, r)

     

从输入r返回元素的iterable长度子序列。